1. Field of the Invention
The invention relates to a voltage regulation method, and especially to a voltage regulation method of a display panel.
2. Description of Related Art
With regard to the liquid crystal display (LCD) panel, each of the gray-level values corresponds to a luminance value. For example, FIG. 1 is a curve diagram of the gray-level value and the luminance value. As show in FIG. 1, the resolution of the LCD panel is equal to 8-bit such that the LCD panel includes 256 gray-level values GL0˜GL255 and 256 corresponding luminance values L0˜L255. In addition, while driving practically, the LCD panel uses the gray-level voltages to rotate the liquid crystal to generate the corresponding luminance value. Therefore, as the curve diagram of the gray-level values and the gray-level voltages shown in FIG. 2, each of the gray-level values has a corresponding gray-level voltage.
Generally, since the contrast ratio of the display panel is based on the maximum luminance value L255 and the minimum luminance value L0, the corresponding minimum gray-level voltage VG0 and the maximum gray-level voltage VG255 are usually set to be two independent voltages, and the rest of the gray-level voltages VG1˜VG254 are obtained from the divided voltages by the resistor string in the source driver. However, the gray-level voltages VG1˜VG254 frequently vary due to the change of the process and the panel characteristic such that the circumstance of the discontinuous gray-level frame occurs on the LCD panel.
In order to deal with the aforementioned problems, the existing voltage regulation method is externally connecting a portion of the connection nodes of the resistor string with a plurality of fixed voltages. Thus, the portion of the gray-level voltages are regulated by external fixed voltages without completely depending on the divided voltages by the resistor string. In addition, the existing voltage regulation method is regulating the fixed voltages by comparing the luminance values as the display panel displays the fixed voltages with the ideal luminance values. However, due to the effect of the leakage light and the noise of the display panel, it is not easy for the optical instrument to measure the exact value of the luminance value corresponding to the low gray-level value. Therefore, the gray-level voltages generated by the resistor string vary significantly such that the display quality of the display panel is affected. The aforementioned problem may be handled by adding external fixed voltages to reform the variation of the gray-level voltages, but the hardware cost of the display panel may be increased. Therefore, it is an important topic of designing the LCD panel nowadays to effectively regulate the gray-level voltages in consideration of the hardware cost.